1. Field of the Invention
This invention relates to carbostyril derivatives and a process for preparing the same. More particularly, this invention relates to carbostyril derivatives represented by the formula (I) hereinafter described, the pharmaceutically acceptable salts thereof, and a process for preparing the carbostyril derivatives of the formula (I).
2. Description of the Prior Art
It is well known that certain carbostyril derivatives exhibit useful pharmaceutical activities. Representative compounds of this type have been disclosed in Journal of Medical Chemistry, Vol. 15, No. 3, pp. 260-266 (1972), Japanese Patent Publication No. 38789/1971 and Chemical Abstracts, 62, 16212e (1965), etc. However, these prior art references do not teach that the compounds having a wide variety of substituents at the 1-, 5- and/or 8-position of the carbostyril or 3,4-dihydrocarbostyril moiety possess an excellent .beta.-adrenoreceptor blocking activity.
Hitherto, various carbostyril compounds have been disclosed as having a .beta.-adrenoreceptor blocking activity. For example, U.S. Pat. Nos. 3,340,266, 3,910,924 and 3,953,456, and German Patent Application DT No. 2,549,889 disclose that carbostyril or 3,4-dihydrocarbostyril derivatives having a (2-hydroxy-3-substituted-amino)propoxy group at the 5-, 6-, 7- or 8-position of the carbostyril or 3,4-dihydrocarbostyril nucleus possess a .beta.-adrenoreceptor blocking activity.
However, these .beta.-adrenoreceptor blocking agents, i.e., .beta.-blockers, are usually contraindication to subject suffering from bronchial asthma and, therefore, it has been desired to develope .beta.-blockers having a high cardioselectivity.
Recently, carbostyril compounds having a (2-hydroxy-3-substituted-amino)propoxy group at the 5-position of the carbostyril nucleus were found to have a cardioselective .beta.-adrenoreceptor blocking activity, as disclosed in German Patent Application DT No. 2,615,406. Such cardioselective .beta.-blockers would be very useful for treatment of cardiac disorders such as angina pectoris, heart arrhythmia and hypertension. The compounds of the present invention were also found to have excellent cardioselectivity better than that of these known compounds and are useful in treatment or prophylaxis of cardiac disorders in subjects suffering also from chronic obstructive lung disease such as bronchial asthma.